1. Field of the Invention
The present invention relates to a control device for an internal combustion engine for an outboard motor.
2. Discussion of Background
Explanation will be given to a conventional example referring to FIGS. 8 and 9. FIG. 8 is a side view showing a total of an outboard motor mounted with a conventional control device for an internal combustion engine.
In FIG. 8, an outboard motor 1 is attached to a stern plate 2a of a boat 2 through a clamp bracket 3. A swivel bracket 5 is rotatably attached to the clamp bracket 3 around a tilting shaft 4, and a drive unit 6 of the outboard motor 1 is connected to the swivel bracket 5. An engine unit 7 is attached to the upper side of the drive unit 6, and a propeller 8 is attached to the lower side thereof.
The swivel bracket 5 is tilted up or tilted down by a tilting cylinder 9. The swivel bracket 5 is controlled to trim by two trimming cylinders 10. A steering bracket 11 rotates the drive unit 6 with respect to the swivel bracket 5 around a steering shaft, not shown, thereby performing the steering.
The tilting cylinder 9 and the trimming cylinders 10 are expanded and retracted by hydraulic pressure from a hydraulic pump driven by an electric motor, not shown, thereby performing the tilting-up or the tilting-down, and a trim angle control. The trim angle control is performed by controlling a rotational direction and a rotational speed of an electric motor. The direction of thrust of the propeller 8 is controlled by the trim angle control in accordance with an inclination and a speed of the boat, thereby obtaining optimum speed, fuel cost and acceleration.
FIG. 9 is a block diagram showing a first conventional control device for an internal combustion engine. In FIG. 9, a reference numeral 12 designates an engine speed detector, 13, an intake quantity detector, 14, a reference angle signal generator, 15, a crank rotational angle signal generator, 16, a microcomputer, 17, a crank angle detector, 18, an ignition timing setter, 19, an ignition signal generator, 20, an electricity generating coil, 21, a diode, 22, an SCR (semiconductor-controlled rectifier), 23, an ignition condenser, 24, an ignition coil and 25, an ignition plug. The crank angle detector 17, the ignition time setter 18 and the ignition signal generator 19 are composed of softwares.
A pulser coil, not shown, is fixed to an engine main body in the engine unit 7. Each of a plurality of permanent magnets provided around a crankshaft opposes the pulser coil once per one rotation of the crankshaft. Accordingly, one pulse of an electric pulse is induced to the pulser coil with respect to each cylinder at every one rotation of the crankshaft.
A ring gear is fixed around a peripheral portion of a rotor, which receives rotational force by a starter at starting-up of the engine. The crank rotational angle signal generator 15 is opposingly provided at the peripheral portion of the ring gear, which is fixably provided to the engine main body. Electric pulses are induced in the crank rotational angle signal generator 15, with a rotation of the crankshaft, which correspond with respective teeth of the ring gear.
Accordingly, the pulser coil 17 generates the pulses with respect to number of cylinders respectively corresponding to fixed angular positions of the crankshaft, in one rotation of the crankshaft, that is, reference angle signals of the crankshaft. Therefore, the pulser coil functions as the reference angle signal generator 14 of the crankshaft. The angular position of the crankshaft can be detected by counting the generated pulse numbers of the crankshaft rotational angle signal generator 15 after the time point of generating the pulses by the pulser coil.
Furthermore, the pulser coil functions as the engine speed detector 12. Since the pulser coil generates the pulses for the number of the cylinders at every rotation of the crankshaft, the rotational speed of the crankshaft, that is, the engine speed can be detected by measuring a period between the generated pulses of the pulser coil.
A throttle opening degree detector composed of a potentiometer as the intake quantity detector 13, generates a voltage in accordance with a rotational angle of a throttle valve which rotates in response to an operational quantity of a throttle wire, and is capable of detecting an opening degree of the throttle valve, that is, an intake quantity to each cylinder.
The microcomputer 16 is fixed to the engine main body, and as shown in FIG. 9, controls the SCR 22 of an CDI (condenser discharge ignition) ignition device by the crank angle detector 17, the ignition timing setter 18 and the ignition signal generator 19.
The crank angle detector 17 detects the angular position of the crankshaft, by counting the generated pulse number of the crank rotational angle signal generator 15 after the time point of the pulse generation by the pulser coil as the reference angle signal generator 14, as mentioned above.
The ignition timing setter 18 is capable of obtaining an optimum ignition timing, since the ignition timing is a function of the engine speed and a mixture ratio of an intake mixture.
The ignition signal generator 19 generates an ignition signal at a time point wherein the crank angle position is situated at the optimum ignition timing, based on the detection results of the crank angle detector 17 and the ignition time setter 18, switches a gate of the SCR 22 which corresponds to the respective cylinders in a conductive state, and generates electric discharge at the ignition plugs 25 of the respective cylinders. Accordingly, by determining a predetermined ignition timing for the ignition time setter 18 by an advance angle control of the microcomputer 16, the ignition can be performed at the optimum ignition timing which does not cause an abnormal combustion in various running conditions of the engine.
In the CDI ignition device, a voltage generated at the electricity generating coil 20 of a magnet is rectified by the diode 21 and begins to charge the ignition condenser 23, and thereafter, the gate of the SCR 22 is in the conductive state by a signal current generated by the ignition signal generator 19. At the same time, by applying abruptly an electric charge accumulated in the ignition condenser 23 to a primary side of the ignition coil 24, a high-tension voltage is generated at a secondary side of the ignition coil 24, thereby enabling the ignition plug 25 to generate the electric discharge.
In the engine for the outboard motor, a torque of the engine is transmitted to the propeller 8 through the crankshaft and a clutch. Generally, as the clutch of the engine for the outboard motor, a dog clutch 26 shown in FIG. 10 is utilized, of which engaging and disengaging is performed by a shift lever. The dog clutch 26 is moved by moving the shift lever, and a clutch claw 27 engages with a forward gear 28 or a reverse gear 29, thereby transmitting the torque of the crankshaft to the propeller 8. Furthermore, the shift lever is composed as incorporating an accelerator. In case that the shift lever position is at a central position, the clutch is connected to a neutral position. In case that the shift lever position is shifted forward (reverse), the clutch is connected to the forward gear (reverse gear). An accelerator opening degree is increased by moving the clutch to the forward (reverse) direction.
FIG. 11 is a block diagram showing a second conventional control device for an internal combustion engine. In FIG. 11, a reference numeral 12 designates the engine speed detector, 13, the intake quantity detector, 14, the reference angle signal generator, 15, the crank angle signal generator, 16, the microcomputer, 17, the crank angle detector, 118, a fuel injection quantity setting generator and 119, an injector. The crankshaft angle detector 17 and the fuel injection quantity setting generator 118 are composed of softwares.
The microcomputer 16 is fixed to the engine main body, and as shown in FIG. 11, controls the injector 119 based on the crank angle detector 17 and the fuel injection quantity setting generator 118.
Furthermore, the fuel injection quantity setting generator 118 controls a fuel injection quantity of the injector 119 based on the engine speed, the intake quantity and the crank angle. That is, the fuel injection quantity setting generator 118 controls the fuel injection quantity by a pulse width of a pulse signal from the fuel injection quantity setting generator 118 to the injector 119.
In the above conventional control devices for an internal combustion engine, when the clutch is shifted from the forward position or from the reverse position to the neutral position and when the torque of the engine is large, the torque in the peripheral direction is large, since a dog clutch claw 27 is engaged with the forward gear 28 or the reverse gear 29 and a torque in the axial direction is required which is larger than that of the torque in the peripheral direction to disengage the dog clutch 26 from the respective gear.
Furthermore, in the above conventional control devices for an internal combustion engine, the accelerator opening degree is inevitably in a fully-closed state, when the clutch is connected to the forward gear (reverse gear) by shifting it from the neutral position. Accordingly, the connection of the clutch is performed in a state wherein the torque of the engine is small, thereby causing an engine stoppage in case that the increase of an engine load initiated by the clutch connection is excessively large.